1. Field of the Invention
The invention relates to a needle device, to a use of such a needle device, and to a method for manufacturing such a needle device.
2. Description of Related Art
In the processing of a planar structure that is referred to as “fibrillation”, a stretched band of synthetic film, made from polypropylene for example, is split by aligning the molecule chains or polymer threads in parallel longitudinal strips. Previously, fibrillation has been performed using a needle roller equipped with radially protruding needles that have a substantially round cross section. The synthetic band is stretched and passed over the rotating needle roller, so that the needles gently prick the band and cause the splitting. However, such needle rollers with round needles do not work well, or fail entirely, with more elastic synthetic materials that contain more polyethylene and fewer parallel chains, for example, as the needles tend to tear the synthetic band because the elastic material does not have splitting properties.
In this context, it is intended to improve a needle device of such kind having round needles in such a manner that it may also be used to fibrillate more elastic synthetic materials.
A needle device of the generic type, comprising a rotatable roller the circumference of which is fitted with triangular blades, each having one cutting edge and the tips of which protrude from the roller, is known from CN 2 889 653 Y. The blades are mounted in dovetail grooves in the roller by means of connecting elements. One disadvantage of this needle device is that mounting and replacing the individual blades in the grooves in the roller is very labour-intensive.